Method for making reinforcing structures for vehicles tyres and a tyre obtained thereby

ABSTRACT

A method for making a reinforcing structure for a vehicle tyre includes laying down at least one continuous thread element onto a support element, generating one or more layers. A path of the at least one thread element is substantially concentric with a rotation axis of the tyre. The at least one thread element is laid down according to an undulated trajectory including a plurality of waves succeeding each other along a line circumferentially extended around the rotation axis of the tyre. A tyre for a vehicle wheel includes a carcass structure, a pair of annular anchoring structures, reinforcing structures disposed at axially opposite side portions of at least one carcass ply of the carcass structure, a belt structure, a pair of sidewalls, and a tread band. Each reinforcing structure includes one or more layers of at least one continuous thread element extending according to the undulated trajectory.

The present invention relates to a method for making reinforcingstructures for vehicle tyres, comprising the step of laying down atleast one continuous thread-like element onto a support element,according to a deposition path substantially concentric with therotation axis of the tyre.

The invention also relates to a tyre integrating reinforcing structuresmade according to said method, said tyre being of the type comprising acarcass structure including at least one carcass ply having its ends inengagement with respective circumferentially inextensible annularanchoring structures; said carcass ply having two axially-opposite sideportions separated from each other by a crown portion and each extendingradially away from one of the annular anchoring structures until saidcrown portion; a belt structure applied to said crown portion at aradially external position relative to the carcass ply; a pair ofsidewalls applied to said side portions at an axially external positionrelative to the surfaces of the carcass ply; a tread band applied to thebelt structure at a radially external position thereof; reinforcingstructures, each comprising at least one continuous thread-like elementextending in an undulated trajectory substantially concentric with therotation axis of the tyre.

Manufacture of tyres for vehicle wheels involves formation of a carcassstructure essentially made up of one or more carcass plies shaped in asubstantially toroidal configuration and having their axially oppositeside edges in engagement with respective annular anchoring structuresintegrating circumferentially inextensible annular inserts usuallyreferred to as “bead rings” placed at the tyre regions usuallyidentified with the name of “beads”.

Applied to the carcass structure, at a radially external position, is abelt structure comprising one or more belt layers in the form of aclosed loop, substantially made up of textile or metallic cords suitablyoriented with respect to each other and to the cords belonging to theadjacent carcass plies.

At a radially external position to the belt structure a tread band isapplied usually comprising a strip of elastomeric material ofappropriate thickness.

It should be pointed out that, to the aims of the present description,by the term “elastomeric material” it is intended blends of rubber intheir entirety, i.e. assemblies formed of at least one base polymersuitably amalgamated with reinforcing fillers and process additives ofvarious types.

Finally, to the opposite sides of the tyre being processed, a pair ofsidewalls is applied each of which covers a side portion of the tyreincluded between a so-called shoulder region, located close to therespective side edge of the tread band, and a so-called bead located atthe corresponding bead-ring.

Tyres are generally classified into at least two categories,differentiated from each other due to the orientation exhibited by thecords being part of the carcass plies. In particular, there are theso-called “radial tyres” in which each of the cords arranged in thecarcass ply or plies lies in a plane substantially radial to therotation axis of the tyre, i.e. has an orientation substantiallyorthogonal to the circumferential extension direction. Then there arethe so-called tyres “of the conventional type” or “cross-ply tyres”, thecarcass structure of which generally comprises at least one carcass plyhaving cords oriented obliquely to the circumferential extensiondirection of the tyre, and a second carcass ply, radially superposed onsaid first ply, the cords of which exhibit a symmetrically-crossedoblique orientation with respect to the cords of the first ply.

Tyres of the radial type, as compared with those of the conventionaltype, offer advantages in terms of lightness, ride comfort, resistanceto wear and structural strength to high speeds. Conversely, they have asidewall of weaker structure than tyres of the conventional type, sothat a possible failure at the sidewall usually involves the tyre beingout of use.

The above features have caused the tyres of the conventional type to bebasically fallen into disuse in those Countries where a modern roadnetwork (minimising the risk of accidental failures to the sidewall) ispresent, in favour of tyres of the radial type.

Development in time of these tyres has led to a progressive reduction intheir section height also for the purpose of obviating the feeling ofride unsteadiness generated by the sidewalls that are radially veryextended.

In particular cases and/or for specific uses requiring that the tyresidewalls should have a higher strength than that offered by the carcassply, also in combination with a reduced section height, the sidewalls ofa tyre is to be strengthened by means of additional reinforcingelements.

In particular, from document U.S. Pat. No. 3,044,522 reinforcement fortyres is known which is assembled on a collapsible drum and subsequentlyapplied to the tyre carcass. The reinforcement is made up of layersaxially disposed in a side-by-side relationship upon interposition of anelastomeric filling element. Each layer is defined by a plurality ofcoils disposed radially in side-by-side relationship and extending in asinuous course having predetermined pitch and width. In addition, thecoils of two distinct layers are circumferentially offset relative toeach other, by about half a pitch.

Document U.S. Pat. No. 3,044,522 in the same manner as many othertraditional production methods, essentially involves that the individualtyre components should be first made separately from each other to bethen assembled during a tyre-building step.

The Applicant's present trend is however that of resorting tomanufacture methodologies enabling production and storage ofsemi-finished articles to be minimised or, if possible, eliminated.

Practically, the research and development studies carried out by theApplicant are oriented to new process solutions allowing the individualcomponents to be made by directly forming them on the tyre being built,preferably following a pre-established sequence.

This is particularly suitable above all in the production of tyres ofthe radial type.

In this connection, production processes have been proposed which aim atobtaining given tyre components, such, for example, as tread band,sidewalls or others, by laying down onto a toroidal support carrying thetyre being worked, a continuous strip-like element of elastomericmaterial having a reduced section as compared with that of the componentto be obtained and disposed to form a plurality of coils around therotation axis of the tyre, which coils are arranged consecutively inside by side relationship and/or superposed on each other so as todefine the component itself in its final configuration.

In the European Patent Application No. 01830350.3 the Applicant hasproposed adoption of annular stiffening inserts placed at the sidewallsof the radial tyres to increase stiffness of same, obtained bycircumferentially winding at least one continuous thread-like elementinto several consecutive turns so as to form a series of coils disposedin radial side by side relationship and concentric with the geometricrotation axis of the tyre.

The Applicant has perceived that, notwithstanding the good resultsachieved with these inserts formed of one or more spiral-woundthread-like elements, there is still an interest in trying to improvetyre performance, in particular as regards increase in the sidewallstiffness of tyres intended for equipping two-wheeled vehicles. In fact,during the ride on a bend these tyres bank with respect to the vertical,according to camber angles of a very high value, thereby submitting thetyre sidewalls to important stresses.

These tyres have a marked transverse curvature at the crown which isnormally defined by the particular value of the ratio between thedistance of the tread centre from the line passing through the laterallyopposite extremities of the tread itself, measured at the equatorialplane of the tyre, and the distance measured along the tyre chordbetween said extremities. In tyres for two-wheeled vehicles the value ofthe curvature ratio is generally at least about 0.15 and usually it isof about 0.3 in the case of rear tyres and also higher, until about0.45, in the case of front tyres, versus a value usually of about 0.05in motor-vehicle tyres.

The Applicant has perceived that, in accordance with the presentinvention, it is possible to increase the sidewall stiffness in radialtyres, while keeping the advantages typical of a tyre of a radialstructure in terms of lightness, ride comfort and structural strength.This is achievable by laying down a continuous thread-like element onthe tyre sidewalls according to an undulated trajectory substantiallyconcentric with the rotation axis of the tyre.

Therefore, it is an object of the present invention to provide a methodfor making reinforcing structures for vehicle tyres, comprising the stepof laying down at least one continuous thread-like element onto asupport element, according to a path substantially concentric with therotation axis of the tyre, characterised by the fact of generating atleast one layer of said at least one continuous thread-like element bylaying down said continuous thread-like element according to anundulated trajectory including a plurality of waves succeeding eachother along a line circumferentially extended around the rotation axisof said tyre.

It is a further object of the invention to provide a tyre for vehiclewheels, characterised by reinforcing structures placed at the sidewallsof said tyre, each including at least one layer of at least onecontinuous thread-like element extending according to an undulatedtrajectory including a plurality of waves succeeding each other along aline circumferentially extended around the rotation axis of said tyre.

In an embodiment of the present invention said at least one continuousthread-like element is laid down in several layers, so that the waves ofthe different layers mutually cross to create a network structure.

The tyre of the present invention can be suitable for either two-wheeledor four-wheeled vehicles, the latter including both cars and theso-called industrial vehicles.

In the present specification and in the claims, the term “supportelement” means the tyre structure upon which the reinforcing structurebeing the object of the present invention is laid down, as betterclarified in the following.

In the present specification and in the claims, the terms “undulated”and “wave” refer both to substantially sinusoidal shapes (withcontinuous bending) and to the so-called zigzag shapes, characterised bybroken lines.

Further features and advantages will become more apparent from thedetailed description of a preferred but not exclusive embodiment of amethod for making reinforcing structures for vehicle tyres, and a tyreincorporating reinforcing structures made in accordance with the presentinvention. This description will be set out hereinafter with referenceto the accompanying drawings, given by way of non-limiting example, inwhich:

FIG. 1 is a fragmentary perspective and split view of a tyre forfour-wheeled vehicles provided with a reinforcing structure accomplishedin accordance with the present invention;

FIG. 2 is an interrupted section taken in a plane radial to the rotationaxis of a tyre for two-wheeled vehicles, showing the cross-sectionoutline of the tyre components;

FIGS. 3 to 6 diagrammatically show a continuous thread-like elementspiral wound up in an undulated trajectory substantially concentric withthe rotation axis of the tyre according to four different embodiments ofthe concerned method;

FIGS. 7 and 8 show two different apparatus adapted to make reinforcingstructures for vehicle tyres in accordance with the present invention.

With reference to the drawings, a tyre having a reinforcing structureobtainable by the method in accordance with the present invention hasbeen generally identified by reference numeral 1.

In the embodiment shown in FIG. 2 concerning a tyre for motor-vehicles,tyre 1 has a right section marked by a high transverse curvature: inmore detail, said tyre 1 has a section height H measured in theequatorial plane between the centre of the tread band and the fittingdiameter identified by the reference line r and passing through the tyrebeads.

In addition, tyre 1 has a width C defined by the distance between thelaterally opposite ends E of the tread itself, and a curvature definedby the particular value of the ratio between the distance f of the treadcentre from the line passing through the extremities E of the treaditself, measured in the equatorial plane of the tyre.

The invention takes a particular importance when applied to tyres fortwo-wheeled vehicles having a section ratio H/C as high as or lower than0.70 and generally also marked by a curvature ratio f/C higher than0.15, although its extent and advantages also apply to tyres of othertypes, those for four-wheeled vehicles for example, whether they arecars or the so-called industrial vehicles.

With reference to FIGS. 1 and 2, tyre 1 comprises a carcass structure 2having at least one carcass ply 3 of a substantially toroidalconformation and engaged, by its axially spaced apart circumferentialedges, with a pair of annular anchoring structures 4 each of which, whentyre 1 is finished, is disposed in the region usually denoted as “bead”.

The carcass ply 3 has two side portions 3 a each extending radially awayfrom one of the annular anchoring structures 4.

Applied to the carcass structure 2, at a circumferentially externalposition, is a belt structure 5 comprising at least one primary beltlayer 6, including one or more continuous parallel cords or otherappropriate thread-like elements, wound into coils 6 a disposed in axialside-by-side relationship and having a constant or varying density (thelatter case being not shown), and oriented at a substantially zero anglewith respect to an equatorial plane of the tyre, as described in PatentU.S. Pat. No. 5,975,175 in the name of the Applicant, for example.Possible auxiliary belt layers 7 a, 7 b (diagrammatically shown in chainline in FIG. 1) can be disposed at a radially internal position relativeto the primary belt layer 6. Circumferentially superposed on the beltstructure 5 is a tread band 8 on which, following a moulding operationcarried out concurrently with vulcanisation of the tyre, longitudinaland/or transverse grooves 8 a disposed to define a desired “treadpattern” can be formed.

Tyre 1 also comprises a pair of so-called “sidewalls” 9 laterallyapplied, on opposite sides, to reinforcing structures 10 as hereinafterdefined, at an axially external position relative to the side portions 3a of the carcass ply 3.

Each of said reinforcing structures 10 comprises at least one layer of acontinuous thread-like element 11 extending in an undulated trajectory11 a around the rotation axis X of tyre 1, and is axially interposedbetween a respective side portion 3 a of the carcass ply 3 and one ofthe sidewalls 9. Preferably, each structure 10 extends between one ofthe annular anchoring structures 4 and a corresponding side edge of thebelt structure 5. In more detail, the side edge of the belt structure 5is preferably in overlapping relationship, by a desired extent, with theradially external end edge of the reinforcing structure 10, asexemplified in FIGS. 1 and 2.

The carcass structure 2 can be possibly coated, on its inner surface,with a so-called “liner” 12, essentially made of at least one air-tightlayer of elastomeric material for ensuring a hermetic seal of tyre 1when inflated.

The present invention can be advantageously put into practice by amethod according to which, except for what described in more detail inthe following of the present specification, assembling of the abovelisted components, as well as production of one or more of same, ispreferably achieved following the teachings proposed in documentEP-A-0976536, in the name of the same Applicant, for example.

Within the manufacturing process of tyre 1, formation of the carcass ply3 can be advantageously carried out by sequentially laying downpreviously cut strip-like elements, consecutively disposed in mutualcircumferential side-by-side relationship on the outer surface of atoroidal support 13 on which liner 12 may have been previously formed.

Accomplishment of tyre 1 involves execution of further working steps,such as application of the belt structure 5 at a position radiallyexternal to the carcass structure 3, application of the tread band 8 ata position radially external to the belt structure 5 and application ofsidewalls 9 on opposite sides of the carcass structure 3, not furtherdescribed as not of importance to the aims of the invention.

The reinforcing structures 10 are laid down before application of thesidewalls and, preferably, also before application of the belt.

Within this manufacturing process, an apparatus to be used for makingthe reinforcing structures 10 of tyre 1 has been denoted by 14 in FIG.7.

To this aim, apparatus 14 essentially comprises a support device 15arranged to engage the toroidal support 13 at an attachment shank 15 acoaxially jutting out from at least one side of said support 13.

Associated with the support device 15 are appropriate devices to drivethe toroidal support 13 in rotation around its geometric axis that, whenthe tyre has been completed, is coincident with the rotation axis X ofthe latter. A pair of deposition members 16 operates on the oppositesides of the toroidal support 13 each for the purpose of carrying outapplication of the continuous thread-like element coming, for example,from a supply reel or directly from an extruder or other suitable supplydevices, not shown because they are not of importance to the aims of theinvention. The continuous thread-like element 11, preferably rubberisedwith a thin layer of elastomeric material, can be made of textile ormetallic material. Preferably it is of textile material, more preferablyselected from the group consisting of nylon andpoly(ethylene-naphthalene-2,6-di-carboxylate), also known as PEN.

Each deposition member 16 essentially comprises an arm 17 carrying anend roller or another type of applying device 18 oriented in an axisradial to the rotation axis X of the toroidal support 13 and arranged toact in thrust relationship against the toroidal support 13 itself toapply the thread-like element 11 and make it adhere to the end flap ofthe carcass ply 3 or other support element, at a given application point18 a.

The arm 17 of each deposition member 16 is carried by a first guidestructure 19 movable in a first movement direction “L”, preferablyparallel to the rotation axis X of the toroidal support 13. The firstguide structure 19 is in turn movable on a second guide structure 20,along a second direction “N” preferably orthogonal to the first movementdirection “L”. These movements result in corresponding movements of theapplying end roller 18 and consequent displacements of the applicationpoint 18 a of the thread-like element 11 on the toroidal support 13.

Each arm 17 is also preferably rotatable about an oscillation axis “K”orthogonal to the movement directions “L” and “N”.

In order to make each of the reinforcing structures 10, it isessentially provided that the applying end roller 18 of each depositionmember 16 should be brought into thrust relationship against the outersurface of the toroidal support 13 to cause application of a first endof the continuous thread-like element 11 against the respective end flapof the carcass ply 3 or other component of tyre 1 previously formed onthe toroidal support itself 13.

Preferably, deposition of the continuous thread-like element 11 ispreceded by deposition onto the carcass ply 3 of a skim coat of suitableelastomeric material. As an alternative to deposition of said skim coat,the strip-like elements constituting the carcass ply 3 are provided withan asymmetric rubberising layer richer in elastomeric material at theouter surface thereof.

Simultaneously with or immediately after application of the first end ofthe continuous thread-like element 11, the toroidal support 13 is drivenin rotation around its geometric axis X. Concurrently with this rotatorymotion, the applying end roller 18 of each deposition member 16, andtherefore the application point 18 a of the respective thread-likeelement 11, is moved close to or away from the rotation axis X in themovement direction N, whereas movements along the oscillation axis “K”and the movement axis “L” ensure a constant thrust relationship of thecontinuous thread-like element 11 against the toroidal support 13.

The applying end roller 18 carries out such a displacement that at leastone layer of the continuous thread-like element is laid down on support13 in an undulated trajectory 11 a substantially concentric with therotation axis X. The undulated trajectory 11 a develops into a pluralityof waves 11 b consecutively disposed along a line “t” circumferentiallyextended around the rotation axis of said tyre. Should the continuousthread-like element 11 be laid down in several layers, the waves 11 b ofone layer would cross those of another, as detailed in the following.

Alternatively, the transverse distribution movement having at least onecomponent perpendicular to axis X is achieved through movement of axis Xof the toroidal support 13 by use of a second type of apparatus, partlyillustrated in FIG. 8 and identified by numeral 21.

In this case, the devices for application of the thread-like element 11can advantageously be fixed devices 22; consequently the applicationpoint is a fixed-point 22 a too.

For the purpose it is provided that the circumferential distributionmeans, designed to drive the toroidal support 13 in rotation around itsown axis X, and the transverse-movement means should be integrated intoa robotized arm 23, partly shown in FIG. 8, arranged to removably engagethe toroidal support 13, preferably in cantilevered fashion, toconveniently move it with respect to the applying devices 22.

Preferably, the robotized arm 23 is a seven-axis anthropomorphous arm,of the type described in WO 00/35666 (in the name of the sameApplicant), for example.

During deposition of the reinforcing structure 10, the robotized arm 23carries out suitable orientation of the toroidal support 13 relative tothe application point 22 a, and drives the support in rotation aroundthe rotation axis X in synchronism with said orientation movements, soas to determine distribution of the thread-like element 11 in at leastone layer, following an undulated trajectory 11 a.

In particular, concurrently with rotation around axis X, the toroidalsupport 13 is moved along directions having at least one componentorthogonal to the axis X itself.

Irrespective of how they are obtained, the undulated trajectories 11 ahave an extension determined by the laws of relative motion between theapplying devices 18 or 22 and the toroidal support 13.

More specifically, the thread-like element 11 extends in an alternatedundulated trajectory 11 a to form waves 11 b having a pitch “p” and awidth “a”, disposed consecutively along a line “t”, as shown in FIGS. 3to 6.

Width “a” and pitch “p”, can be constant or variable in an independentmanner both in each layer and, in case, in the different depositionlayers of the continuous thread-like element 11.

Line “t”, of a predetermined diametrical size “d”, describes a path in aplane normal to the rotation axis of tyre 1, along which the undulateddeposition trajectory 11 a of the thread-like element 11 extends, aroundthe rotation axis X of the tyre itself. When the thread-like element 11is provided in more than one layer, the layers can be laid down in anundulated trajectory 11 a and line “t” may be of a varying or constantdiametrical size “d”.

If the continuous thread-like element 11 is laid down in several layers,and pitch “p” does not correspond to an exact sub-multiple of thecircumferential extension of line “t”, the waves 11 b of each layer willbe offset relative to those of other layers, so that a plurality ofcrossing points will be formed, at which the thread-like element 11 issuperposed upon itself to create a network structure on the side portion3 a of tyre 1.

By way of example, as shown in FIGS. 3 and 4, in all the depositionlayers the thread-like element 11 may be provided to follow trajectories11 a having a substantially circular single line “t”, concentric withaxis X of tyre 1.

More specifically as regards FIG. 3, each layer has an undulatedtrajectory 11 a of sinusoidal course, with waves 11 b that arecircumferentially offset with respect to those of other layers by avalue different from, and in this case lower than, their distributionpitch “p”. In this way the waves 11 b of each layer arecircumferentially shifted relative to the waves 11 b of other layers tocreate a series of crossing points and, therefore, the above mentionednetwork structure.

According to this first embodiment, the width “a” of the sinusoid isconstant in all the deposition layers and is coincident with the radialextension of the reinforcing structure 10.

In a second embodiment shown in FIG. 4, the undulated trajectory 11 a isprovided in segments of a broken line substantially disposed at an acuteangle with respect to each other, to give origin to a zigzag trajectory.

In this second embodiment too the undulated trajectory 11 a keeps on aline “t” of constant diametrical sizes “d” for each layer, and theradial extension of the annular reinforcing structure 10 is determinedby width “a” that too is constant for all layers.

In a third embodiment shown in FIG. 5, line “t” (not specifically shown)is a spiral, i.e. it has a varying, in this case growing, diametricalsize “d”. Also the width “a” of the waves 11 b is variable and, still inthis case, is smaller than the radial extension of the reinforcingstructure 10. Herein, the radial extension of the reinforcing structure10 is given by the diametrical size “d”of the radially innermost andradially outermost line “t”, and also by width “a” of the radiallyinnermost and radially outermost layers.

FIG. 6 shows an example of a thread-like element 11 laid down in asingle layer. In this case, the undulated trajectory 11 a is formed of aplurality of sinusoidal waves 11 b, of a constant width “a”corresponding to the radial extension of the reinforcing structure 10,and a pitch “p” which is also constant and corresponds to one fifth ofthe pitch shown in FIG. 3.

The present invention achieves important advantages.

A deposition carried out in accordance with the method in referenceenables a greater stiffness of the tyre sidewalls to be achieved.

In addition, a deposition carried out in accordance with the method inreference provides further variables, such as pitch “p”, width “a”, thewave shape and the trajectory of line “t”, for managing the radialextension of the reinforcing structure and the circumferential densityof the thread-like element and, consequently, the stiffness of saidsidewalls.

In particular, the method of the present invention allows stiffeningside structures to be made for radial tyres which have a high sectionratio, in particular tyres for motorcycles of the “custom” type, forexample.

It should be also recognised that the invention, while described withparticular reference to accomplishment of reinforcing structures forsidewalls, lends itself to be put into practice in order to make othertypes of reinforcing structures as well, to be integrated into thestructure of a tyre.

Finally, it is to be noted that accomplishment of these reinforcingstructures can be also obtained separately of the tyre being processed,on a toroidal support or a support of other type, for a subsequentapplication to said tyre.

1-20. (canceled).
 21. A method for making a reinforcing structure for a vehicle tyre, comprising: laying down at least one continuous thread element onto a support element; wherein laying down the at least one thread element generates one or more layers of the at least one thread element, wherein a path of the at least one thread element is substantially concentric with a rotation axis of the tyre, wherein the at least one thread element is laid down according to an undulated trajectory, and wherein the undulated trajectory comprises a plurality of waves succeeding each other along a line circumferentially extended around the rotation axis of the tyre.
 22. The method of claim 21, wherein the support element comprises at least one carcass ply.
 23. The method of claim 22, further comprising coating the at least one carcass ply with a skim coat.
 24. The method of claim 22, wherein the at least one carcass ply comprises strip elements, and wherein the method further comprises rubberizing the strip elements to a greater extent at a radially external surface of the strip elements.
 25. The method of claim 21, wherein the undulated trajectory comprises a plurality of substantially sinusoidal waves.
 26. The method of claim 21, wherein the undulated trajectory comprises a plurality of waves in a zigzag shape.
 27. The method of claim 21, wherein laying down the at least one thread element generates several layers of the at least one thread element, and wherein each layer is generated by laying down the thread element according to the undulated trajectory circumferentially developed along a line common to all of the several layers.
 28. The method of claim 21, further comprising developing the trajectory according to a substantially circular line.
 29. The method of claim 21, wherein laying down the at least one thread element generates two or more layers of the at least one thread element, and wherein the method further comprises developing the trajectory according to a line of a different circumferential extension in at least two of the layers.
 30. The method of claim 21, further comprising developing the trajectory according to waves of constant pitch.
 31. The method of claim 21, further comprising developing the trajectory according to waves of constant width.
 32. The method of claim 21, wherein the method is carried out on a toroidal support by alternately shifting an application point of the at least one thread element along a movement direction radial to a rotation axis of the toroidal support, while the toroidal support is driven in rotation around the rotation axis of the toroidal support.
 33. A tyre for a vehicle wheel, comprising: a carcass structure; a pair of circumferentially inextensible annular anchoring structures; reinforcing structures disposed at axially opposite side portions of at least one carcass ply of the carcass structure at axially external positions relative to the at least one carcass ply; a belt structure applied to a crown portion of the at least one carcass ply at a radially external position relative to the at least one carcass ply; a pair of sidewalls applied to the reinforcing structures at axially external positions relative to respective reinforcing structures; and a tread band applied to the belt structure at a radially external position of the belt structure; wherein ends of the carcass structure are engaged with respective annular anchoring structures, wherein the side portions of the at least one carcass ply are separated from each other by the crown portion of the at least one carcass ply, wherein each side portion extends radially away from one of the annular anchoring structures toward the crown portion, wherein each reinforcing structure comprises one or more layers of at least one continuous thread element extending according to an undulated trajectory, and wherein the undulated trajectory comprises a plurality of waves succeeding each other along a line circumferentially extended around a rotation axis of the tyre.
 34. The tyre of claim 33, wherein the undulated trajectory comprises a plurality of substantially sinusoidal waves.
 35. The tyre of claim 33, wherein the undulated trajectory comprises a plurality of waves succeeding each other in a zigzag shape.
 36. The tyre of claim 33, wherein each reinforcing structure comprises several layers of the at least one thread element, and wherein the at least one thread element in each layer is distributed according to the undulated trajectory circumferentially developed along a line common to all of the several layers.
 37. The tyre of claim 33, wherein the line is of substantially circular shape.
 38. The tyre of claim 33, wherein each reinforcing structure comprises two or more layers of the at least one continuous thread element extending according to the undulated trajectory, and wherein the line comprises a different circumferential extension in at least two of the layers.
 39. The tyre of claim 33, wherein a pitch of the waves is constant along the line.
 40. The tyre of claim 33, wherein a width of the waves is constant along the line. 